Impact of Hydration Levels on Respiratory Aerosol Emissions

MAHENDER SINGH RAWAT, Dinushani Senarathna, Byron Erath, Sumona Mondal, Sarah K. Sirsat, Andrea Ferro, Clarkson University

     Abstract Number: 521
     Working Group: Bioaerosols

Abstract
Investigations of aerosol emission and particle size distributions during phonation have confirmed that emission rates can vary tremendously; over two orders of magnitude. Prior work has shown that variables such as loudness, frequency, and age influence the emission rates. Nevertheless, these factors do not entirely explain the wide disparity observed in emission rates.

To overcome this knowledge gap, we experimentally evaluated the effect of hydration level on respiratory aerosol emissions. This study proposes that well-hydrated (Hy) individuals produce more respiratory aerosols during vocalization than dehydrated (Dhy) individuals, as dehydration decreases saliva and respiratory tract lining fluid production and modifies the rheology of these fluids.

To investigate this hypothesis, we measured respiratory aerosol emissions during phonation from participants in both a hydrated and dehydrated state. Aerosol measurements were recorded by at TSI (Shoreline, MN, USA) Model 3321 Aerodynamic Particle Sizer (APS) while expiratory flow was measured using a well-sealed, half mask connected to an iWorx (Dover, NH) TA Model 220 spirometer.

Each participant performed the same vocal exercises in a randomized order that included the open vowel /a/, forced breathing at a similar flow rate as the open vowel /a/, running speech, and normal breathing. Based on our preliminary results from 15 participants (9 females and 6 males), we observed that during vocal activities, participants in a dehydrated state emitted approximately 15% fewer particles, both in terms of particle number emission rate and concentration, compared to when they were hydrated. This trend was consistent for particles ranging in size from 0.5 to 20 microns. Depending on the hydration condition, 1-3 of the 15 participants were identified as extreme outliers, with emission rates exceeding the third quartile (75th percentile value) plus three times the interquartile range.